Pre-exposure prophylaxis (PrEP) is an HIV prevention strategy in which HIV medicines are used by a person before they are exposed to HIV in order to decrease his or her chance of getting infected. In this study, we will investigate a new PrEP strategy in women using a drug called maraviroc, a medicine used in the treatment of HIV infection called a CCR5 antagonist. We hypothesize that maraviroc could be a particularly good drug for PrEP because it achieves high concentrations in the genital tract in women and decreases the number of HIV-susceptible cells in the genital tract, and thus could potentially be dosed in more favorable ways than the current PrEP drugs.